Cartilage is a tissue composed of a cartilage matrix and cartilage cells (chondrocytes) spotted therein. The cartilage matrix is composed of water, collagen, proteoglycan, and others. Proteoglycan is a complex composed of a polysaccharide called glycosaminoglycan, and a protein. Cartilage fulfills various functions in the living body through the elasticity thereof.
Diseases due to a cartilage damage include various diseases such as arthrosis deformans, arthritis and rheumatism. As therapeutic agents for these diseases, many effective components such as glucosamine (see Non-Patent Document 1) and glucuronic acid (Patent Document 1) are known.
Fucoidan is a polysaccharide contained in marine alga (for example, mozuku (Nemacystus decipiens), Japanese kelp (Laminaria japonica) etc.), and has been ingested from early times by eating of these marine alga. Fucoidan has many physiological activity functions such as immunostimulatory activity, adhesion-preventing activity and anti-inflammatory activity (see Patent Documents 2 and 3, and others).
Patent Document 4 describes that fucoidan promotes a morphogenetic action of bone and cartilage. However, the disclosure of Patent Document 4 is merely about an agent for promotion of osteogenesis. Osteoblast is necessary to induce bone, and chondroblast is necessary to induce cartilage. Osteoblast and chondroblast are each derived by differentiation or induction from undifferentiated cells in accordance with different systems. Osteoblast and chondroblast are entirely different cells, and are also different from each other in their properties and functions. Osteoblast produces type I collagen, and calcifies it with alkaline phosphatase activity, so as to ossify. Chondroblast, which is cartilage cell precursor, produces type II collagen or glycosaminoglycan and is differentiation-induced to cartilage cell. The cartilage cell synthesizes proteoglycan around the cells, thereby blocking calcification and bone formation based on osteoblast to form cartilage. For the formation of cartilage, ossification is required to be inhibited. The cartilage formation is a promoting of synthesis of proteoglycan by cartilage cell. Thus the cartilage formation is a biological phenomenon which is entirely different from the bone formation. In other words, Patent Document 4 discloses a reverse effect to a matter that fucoidan promotes the formation of cartilage.
In Examples of Patent Document 4, results obtained by administering fucoidan or the like directly into established cell lines are disclosed. However, according to any ordinary administering manner such as oral ingestion, fucoidan is never directly contacted with osteoblast. In conclusion, Patent Document 4 never discloses what effect is produced when fucoidan is administered into an actual living body.
As described above, there has not been any finding that fucoidan itself has an effect of promoting a chondrogenesis.
Patent Document 1: JP-A-2004-10533
Patent Document 2: JP-A-2005-82806
Patent Document 3: JP-A-2005-508893
Patent Document 4: JP-A-2004-10533
Non-Patent Document 1: Tamai et al., Carbohydrate Polymers, 2002, vol. 48, pp. 369-378